1. Field of the Invention
The present invention relates to an encoding method and an encoding apparatus that allow lossless encoding for picture data composed of pixel data whose number of quantizer bits is larger than eight bits to be effectively and losslessly encoded, and to a decoding method and a decoding apparatus corresponding to the encoding method and the encoding apparatus.
2. Description of the Related Art
In recent years, a digital cinema system that shows a movie by reproducing picture data for example from a picture server and projecting the reproduced picture data on a screen has been developed for movie theaters. In this system, picture data that have been encoded are distributed through a network or recorded on a record medium such as a large capacity optical disc and then provided to the picture server. The picture data are transferred from the picture server to the projector. Thereafter, the projector projects the picture to the screen.
It is preferred that picture data that necessitate high quality such as picture data supplied for such a digital cinema system be encoded by so-called loss-less encoding of which data are not lost in the encoding process and baseband digital video data can be perfectly restored when they are decoded.
As an example of such loss-less encoding, a technology of which a difference value between the current picture data and the immediately preceding picture data is rearranged in the unit of a bit and the resultant data are encoding by the run-length process and Huffman encoding process is described in Japanese Patent Application Laid-Open No. HEI 10-190478 (hereinafter this related art is referred to as patent document 1).
In addition, when picture data necessitate high quality, gradational information of one pixel also necessitates high resolution. The gradational information of a pixel is generally represented by the number of quantizer bits of a pixel. Although the number of quantizer bits of a pixel used for example for personal computers is eight, high quality picture data necessitates a resolution of larger than eight bits, for example 10 bits or 12 bits.